In a question and answer session with financial analysts during Wednesday’s second quarter earnings call, Apple COO Tim Cook revealed that iPod touch sales have “more than doubled year over year.” Combined, iPhone and iPod touch sales total about 37 million units.

Cook called that combined number an “enormous platform for developers,” adding that with the recent changes introduced with Apple’s iPhone 3.0 SDK, which went beta in March and is expected to be released to customers this summer, Apple and its development partners will soon “unleash a whole new level of innovation that keeps Apple years ahead of everyone else.”

In a later question, Cook again referred to the iPod touch, calling it “a runaway hit” whose success is “clearly driven by the App Store.” To that end, Apple CFO Peter Oppenheimer indicated that one of the reasons the iPod touch has been so successful is as a games device.

“All genres [on the App Store] are very popular,” said Oppenheimer, “but games are quite popular. That’s one of the reasons the iPod touch has been such a success.”

Overall, Apple continues to steamroll the competition when it comes to marketshare for digital music players. A recent report from NPD shows that Apple maintains more than 70 percent of the market in the United States alone, and continues to gain share in worldwide markets year-over-year.

In his preamble, Oppenheimer said the App Store now totals more than 35,000 applications.

Cook said that Apple expects to sell its one billionth application on the App Store sometime on Thursday, April 23rd — only nine months after the store first went online to sell software to iPhone and iPod touch users.

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